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31-415: Pelycosaur ( / ˈ p ɛ l ɪ k ə ˌ s ɔːr / PEL -ih-kə-sor ) is an older term for basal or primitive Late Paleozoic synapsids , excluding the therapsids and their descendants. Previously, the term mammal-like reptile had been used, and pelycosaur was considered an order , but this is now thought to be incorrect and outdated. Because it excludes the advanced synapsid group Therapsida ,

62-571: A group of synapsids that have direct ancestral links with the mammals , having differentiated teeth and a developing hard palate. The pelycosaurs appeared during the Late Carboniferous and reached their apex in the early part of the Permian , remaining the dominant land animals for some 40 million years. A few continued into the Capitanian , but they experienced a sharp decline in diversity in

93-404: A majority of systematists since the 1990s, but several paleontologists nevertheless continue using this word. The following classification was presented by Benton in 2004. Basal (phylogenetics) While there must always be two or more equally "basal" clades sprouting from the root of every cladogram, those clades may differ widely in taxonomic rank , species diversity , or both. If C

124-698: A mix of archaic and apomorphic (derived) features that have only been sorted out via comparison with other angiosperms and their positions within the phylogenetic tree (the fossil record could potentially also be helpful in this respect, but is absent in this case). The cladogram below is based on Ramírez-Barahona et al. (2020), with species counts taken from the source indicated. Amborellales (1 species) Nymphaeales (about 90 species) Austrobaileyales (about 95 species) Magnoliids (about 9,000 species) Chloranthales (about 80 species) Monocots (about 70,000 species) Ceratophyllales (about 6 species) Eudicots (about 175,000 species) Within

155-468: A sister group to Homininae and are the basal genus in the great ape family Hominidae as a whole. Orangutans ( Pongo spp.) Humans ( Homo sapiens ) Chimpanzees ( Pan spp.) Gorillas ( Gorilla spp.) Subfamilies Homininae and Ponginae are both basal within Hominidae, but given that there are no nonbasal subfamilies in the cladogram it is unlikely the term would be applied to either. In general,

186-405: A statement to the effect that one group (e.g., orangutans) is basal, or branches off first, within another group (e.g., Hominidae) may not make sense unless the appropriate taxonomic level(s) (genus, in this case) is specified. If that level cannot be specified (i.e., if the clade in question is unranked) a more detailed description of the relevant sister groups may be needed. As can be seen, the term

217-461: A trait generally viewed as ancestral among the apes. Given that the deepest phylogenetic split in a group is likely to have occurred early in its history, identification of the most basal subclade(s) in a widely dispersed taxon or clade can provide valuable insight into its region of origin; however, the lack of additional species in a clade is not evidence that it carries the ancestral state for most traits. Most deceptively, people often believe that

248-553: Is a basal clade of extant angiosperms , consisting of the most species, genus, family and order within the group that are sister to all other angiosperms (out of a total of about 250,000 angiosperm species). The traits of Amborella trichopoda are regarded as providing significant insight into the evolution of flowering plants; for example, it has "the most primitive wood (consisting only of tracheids ), of any living angiosperm" as well as "simple, separate flower parts of indefinite numbers, and unsealed carpels". However, those traits are

279-535: Is a paraphyletic taxon because it excludes the therapsids . For that reason, the term is sometimes avoided by proponents of a strict cladistic approach. Eupelycosauria is used to designate the clade that includes most pelycosaurs, along with the Therapsida and Mammalia. In contrast to "pelycosaurs", Eupelycosauria is a proper monophyletic group. Caseasauria is a pelycosaur side-branch, or clade, that did not leave any descendants. The pelycosaurs appear to have been

310-403: Is a basal clade within D that has the lowest rank of all basal clades within D , C may be described as the basal taxon of that rank within D . The concept of a ' key innovation ' implies some degree of correlation between evolutionary innovation and diversification . However, such a correlation does not make a given case predicable, so ancestral characters should not be imputed to

341-538: Is a cladogram modified from the analysis of Benson (2012): Tseajaia campi Limnoscelis paludis Captorhinus spp. Protorothyris archeri Ophiacodontidae Varanopidae Caseasauria Ianthodon schultzei Ianthasaurus hardestiorum Glaucosaurus megalops Lupeosaurus kayi Edaphosaurus boanerges Edaphosaurus novomexicanus Haptodus garnettensis Pantelosaurus saxonicus Therapsida Sphenacodontidae [REDACTED] This Synapsida -related article

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372-462: Is a family of mostly large (up to 3 m (9.8 ft) or more) Late Carboniferous to Early Permian synapsids . Edaphosaur fossils are so far known only from North America and Europe . They were the earliest known herbivorous amniotes and, along with the Diadectidae , the earliest known herbivorous tetrapods . The head is small in relation to the bulky body, and there is a tall sail along

403-407: Is easy to identify a basal clade in such a cladogram, the appropriateness of such an identification is dependent on the accuracy and completeness of the diagram. It is often assumed in this example that the terminal branches of the cladogram depict all the extant taxa of a given rank within the clade; this is one reason the term basal is highly deceptive, as the lack of additional species in one clade

434-415: Is likely a source of the mis-use of the term. Other famous examples of this phenomenon are the oviparous reproduction and nipple-less lactation of monotremes , a clade of mammals with just five species, and the archaic anatomy of the tuatara , a basal clade of lepidosaurian with a single species. The flowering plant family Amborellaceae , restricted to New Caledonia in the southwestern Pacific,

465-515: Is not reflective of ancestral states or proximity to the common ancestor of extant species. In this example, orangutans differ from the other genera in their Asian range. This fact plus their basal status provides a hint that the most recent common ancestor of extant great apes may have been Eurasian (see below), a suggestion that is consistent with other evidence. (Of course, lesser apes are entirely Asiatic.) However, orangutans also differ from African apes in their more highly arboreal lifestyle,

496-544: Is not used formally, since it does not constitute a group of all organisms descended from some common ancestor (a clade ), because the group specifically excludes the therapsids which are descended from pelycosaurs. Instead, it represents a paraphyletic "grade" of basal synapsids leading up to the clade Therapsida. In 1940, the group was reviewed in detail, and every species known at the time described, with many illustrated, in an important monograph by Alfred Sherwood Romer and Llewellyn Price . In traditional classification,

527-567: Is taken as evidence of morphological affinity with ancestral taxa. Additionally, this qualification does not ensure that the diversity of extinct taxa (which may be poorly known) is represented. In phylogenetics, the term basal cannot be objectively applied to clades of organisms, but tends to be applied selectively and more controversially to groups or lineages thought to possess ancestral characters, or to such presumed ancestral traits themselves. In describing characters, "ancestral" or " plesiomorphic " are preferred to "basal" or " primitive ",

558-418: Is unnecessary and misleading. The term is more often applied when one branch (the one deemed "basal") is less diverse than another branch (this being the situation in which one would expect to find a basal taxon of lower minimum rank). The term may be equivocal in that it also refers to the direction of the root of the tree, which represents a hypothetical ancestor; this consequently may inaccurately imply that

589-586: The great apes , gorillas (eastern and western) are a sister group to chimpanzees , bonobos and humans . These five species form a clade, the subfamily Homininae (African apes), of which Gorilla has been termed the basal genus. However, if the analysis is not restricted to genera, the Homo plus Pan clade is also basal. Humans ( Homo sapiens ) Bonobos ( Pan paniscus ) Chimpanzees ( Pan troglodytes ) Eastern gorillas ( Gorilla beringei ) Western gorillas ( Gorilla gorilla ) Moreover, orangutans are

620-441: The opossums , and other marsupials , and as regular dermal armour with underlying bone in the armadillo . At least two pelycosaur clades independently evolved a tall sail , consisting of elongated vertebral spines: the edaphosaurids and the sphenacodontids . In life, this may have been covered by skin, and likely functioned as a thermoregulatory device or as a mating display . In phylogenetic nomenclature, "Pelycosauria"

651-498: The back, which may have functioned as a thermoregulatory device. The interrelationships of Edaphosauridae was investigated in details by David M. Mazierski and Robert R. Reisz (2010). The cladogram below is modified after their phylogenetic analysis. Ianthasaurus hardestiorum Glaucosaurus megalops Lupeosaurus kayi Edaphosaurus novomexicanus Edaphosaurus colohistion Edaphosaurus boanerges Edaphosaurus cruciger Edaphosaurus pogonias Below

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682-457: The direction of migration away from the area of origin can also be inferred (as in the Amaurobioides and Noctilionoidea cases below). As with all other traits, the phylogeographic location of one clade that connects to the root does not provide information about the ancestral state. Examples where such unjustified inferences may have been made include: Edaphosauridae Edaphosauridae

713-458: The grouping that encompasses all constituent clades except for the basal clade(s) of the lowest rank within a larger clade, exemplified by core eudicots . No extant taxon is closer to the root than any other. A basal group in the stricter sense forms a sister group to the rest of the larger clade, as in the following case:   Basal clade #1  Non-basal clade #1  Non-basal clade #2    Non-basal clade #3 While it

744-670: The late Kungurian . They were succeeded by the therapsids . Some species were quite large, growing to a length of 3 metres (10 ft) or more, although most species were much smaller. Well-known pelycosaurs include the genera Dimetrodon , Sphenacodon , Edaphosaurus , and Ophiacodon . Pelycosaur fossils have been found mainly in Europe and North America , although some small, late-surviving forms are known from Russia and South Africa . Unlike lepidosaurian reptiles, pelycosaurs might have lacked reptilian epidermal scales . Fossil evidence from some varanopids shows that parts of

775-437: The latter of which may carry false connotations of inferiority or a lack of complexity. The terms ''deep-branching'' or ''early-branching'' are similar in meaning, and equally may misrepresent extant taxa that lie on branches connecting directly to the root node as having more ancestral character states. Despite the ubiquity of the usage of basal , systematists try to avoid its usage because its application to extant groups

806-419: The members of a less species-rich basal clade without additional evidence. In general, clade A is more basal than clade B if B is a subgroup of the sister group of A or of A itself. In the context of large groups, the term "basal" is often used loosely to refer to positions closer to the root than the majority, and in such cases, expressions like "very basal" can appear. A 'core clade' refers to

837-485: The order Pelycosauria is paraphyletic in that the therapsids (the "higher" synapsids) have emerged from them. That means Pelycosauria is a grouping of animals that does not contain all descendants of its common ancestor, as is often required by phylogenetic nomenclature . In evolutionary taxonomy , Therapsida is a separated order from Pelycosauria, and mammals (having evolved from therapsids) are separated from both as their own class. This use has not been recommended by

868-524: The sister group of a more species-rich clade displays ancestral features. An extant basal group may or may not resemble the last common ancestor of a larger clade to a greater degree than other groups, and is separated from that ancestor by the same amount of time as all other extant groups. However, there are cases where the unusually small size of a sister group does indeed correlate with an unusual number of ancestral traits, as in Amborella (see below). This

899-445: The skin were covered in rows of osteoderms , presumably overlain by horny scutes . The belly was covered in rectangular scutes, looking like those present in crocodiles . Parts of the skin not covered in scutes might have had naked, glandular skin like that found in some mammals. Dermal scutes are also found in a diverse number of extant mammals with conservative body types, such as in the tails of some rodents , sengis , moonrats ,

930-418: The term is paraphyletic and contrary to modern formal naming practice. Thus the name pelycosaurs , similar to the term mammal-like reptiles , had fallen out of favor among scientists by the 21st century, and is only used informally, if at all, in the modern scientific literature. The terms stem mammals , protomammals , and basal or primitive synapsids are instead used where needed. The modern word

961-403: Was created from Greek [[[wikt:πέλυξ|pélyx]]] Error: {{Lang}}: Non-latn text/Latn script subtag mismatch ( help ) meaning 'basin' and [[[wikt:σαῦρος|saûros]]] Error: {{Lang}}: Non-latn text/Latn script subtag mismatch ( help ) meaning 'lizard'. The term pelycosaur has been fairly well abandoned by paleontologists because it no longer matches the features that distinguish a clade. Pelycosauria

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